U.S. Pat. No. 5,164,734 of Duane G. Fredericks et al. disclosed and claimed an apparatus for producing an electromagnetic signal which contained: (a) means for receiving a radar signal which has frequency of from about 10 to about 94 gigacycles, (b) means for decreasing the frequency of said radar signal by at least about 65 percent, thereby producing a reduced frequency electromagnetic signal with a center frequency of from about 700 to about 1,300 megacycles; (c) delay means for delaying said reduced frequency electromagnetic signal by at least about three radar pulse widths and from about 5 to about 100 microseconds, thereby producing a delayed electromagnetic signal wherein the delay means is comprised of a first delay circuit and a second delay circuit, each of which is substantially non-attenuating and non-dispersive, (d) means for increasing the frequency of said delayed electromagnetic signal to produce a delayed electromagnetic wave with an increased frequency which is substantially identical to the frequency of said radar signal, thereby producing a delayed radar signal of from about 1 to about 94 gigagcycles; (e) means for modulating said delayed radar signal with a frequency of from about 1 to about 94 gigacycles, thereby producing a modulated, delayed radar signal; and (f) means for transmitting said modulated, delayed radar signal. The entire disclosure of this United States patent is hereby incorporated by reference into this specification.
However, the device claimed in U.S. Pat. No. 5,164,732 was operable only over a relatively narrow bandwidth and, because it utilized down conversion, produced spurious emissions. It is an object of this invention to produce a radar target with delayed reply means that overcomes these limitations.
In accordance with this invention, there is provided a radar target with delayed reply means. The radar target comprises: (a) means for receiving a radar signal which has a frequency of from about 0.5 to about 94 gigahertz; (b) means for phase coherently amplitude modulating a continuous wave light emission with said radar signal with said frequency of from about 1 to about 94 gigahertz, thereby producing an phase coherent amplitude modulated light pulse; (c) fiber optic delay means for delaying said amplitude modulated light pulse for at least about one radar pulse width, thereby producing a delayed amplitude modulated light pulse; (d) means for detecting said delayed modulated amplitude modulated light pulse, thereby producing a detected amplitude modulated light pulse; (e) means for converting said detected amplitude modulated light pulse into a converted radio frequency pulse; (f) means for modulating said converted radio frequency pulse, thereby producing a delayed modulated radio frequency pulse, and (g) means for transmitting said delayed modulated radio frequency pulse.